Explanation:
This month, the
Mars Exploration
Rovers are celebrating their 5th
anniversary of operations on the surface of the Red Planet.
The serene
sunset view, part of their extensive legacy of
images from the martian
surface, was recorded by the Spirit rover on May 19, 2005.
Colours in the image have been slightly exaggerated but
would likely be apparent to a human
explorer's eye.
Of course, fine martian dust particles suspended in the thin atmosphere
lend
the sky a reddish colour,
but the dust also scatters blue light in the forward direction,
creating a bluish sky glow near the setting Sun.
The Sun is setting behind the
Gusev crater rim wall some 80 kilometres
(50 miles)
in the distance.
Because Mars is farther away, the Sun is less bright and
only about two thirds the size seen from planet Earth.